MORPHOLOGY

·         Gram – negative rods

·         uncapsulated (except S. typhi)

·         unsporulated sporulaţi

·         Peritrichous flagella

Culture properties:

·         They are aerobe, anaerobe and facultative.

·         On simple media they grow easily.

·         Selective and differential media contain biliary salts and lactose due to wich they grows like the negative lactose-negative “S” colonies.

·         Colonies appearance is like cat eys.

·         Produce H2S.

Diagnosis:

·         Diagnosis is done by culturing the appropriate specimen.

·         Specimens of feces, blood and other sample are culture on selective and non-selective media like blood agar, MacConkey, eosin methylene blue, bimuth sulfite, hektoen .

·         Enrichment media also used exp.  Selenite or tetrathionate.

·         Serotypes are identified by serological tests.

·         The biochemical identification than confirmed by the detection of O and H antigen using polyvalent and specific Antisera.

(Monica2000)